This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C xc2xa7119 from an application entitled Display Device earlier filed in the Korean Industrial Property Office on 28, Feb. 2001, and there duly assigned Serial No. 01-10528 by that Office.
1. Field of the Invention
The present invention relates in general to a display apparatus, and more particularly, to a display apparatus having a function of gamma correcting a video input signal so as to allow a video output signal to have an ideal brightness.
2. Description of the Related Art
Conventionally, a display apparatus receives a video synchronizing signal and an RGB video signals applied from a video card, amplifies the RGB video signals through a pre-amplifier and a main amplifier and displays the amplified signals on the screen of the display apparatus. The brightness comparative to an input voltage level is to be output on the display apparatus.
FIG. 4 shows a brightness graph illustrating changes of the brightness vs. the input voltage level, having a horizontal axis for the video signal applied from a video signal source such as a computer, etc. and a vertical axis for the brightness output in the display apparatus. Referring to FIG. 4, it is desirable that an output of the display apparatus has a brightness curve 51b straight in proportion to a voltage level of the video signal input; however, the output for the input voltage level in a certain section, that is, an actual brightness value is much less than the ideal brightness value, as shown by brightness curve 51a. Such brightness curve is caused by loss of signals in the course of amplification of the respective R, G and B video signals in the main amplifier, errors of parts of the amplifiers, illumination efficiency of displaying elements, etc.
Thus, the video signal supply source such as a computer, etc. has employed a method of amplifying the video signals in advance with gamma correction and applying the corrected signals to the display apparatus.
However, a rate of attenuation of the video signals are different in the respective display apparatuses in the course of treating the video signals, whereas the computer supplies the video signals gamma corrected in a uniform manner. Thus, an optimal brightness cannot be output due to an inherent attenuation property of a display apparatus although the gamma corrected video signals are input.
In addition, there is a problem in that such display apparatuses for medical machines or book searches are unable to reproduce the brightness of the video signals because their video signal supply sources have no function for gamma correction.
Accordingly, the present invention has been made keeping in mind the above-described problems, and an object of the present invention is to provide a display apparatus enabling an optimal output of input video signals through gamma correction in the display apparatus itself.
Another object of the present invention is to provide a display apparatus allowing a user to select whether to do the gamma correction or to select an amount of correction in the display apparatus as described by the user.
These and other objects of the present invention may be accomplished by the provision of a display apparatus, comprising a gamma correction part for gamma correcting an input video signal; a selection input part for selecting the amount of correction by the gamma correction part; and a micro-control unit for controlling the correction amount by the gamma correction part depending upon a selection from the selection input part.
Here, the selection input part is comprised of OSD (on-screen display) control buttons for controlling a display screen.
Preferably, the gamma correction part is comprised of a plurality of gamma section parts for receiving the video signals having predetermined upper limits, or less, and gamma correcting the video signals; a mixer for composing the video signals gamma corrected by the gamma section parts.
Desirably, each of the gamma section parts is comprised of a plurality of signal amplifier parts sectioned into a plurality of sections depending upon the voltage levels of the video signals, for receiving the video signals having the predetermined upper limits, or less, corresponding to the respective sections and amplifying them at predetermined rates; a signal converter part converting the video signal amplified in each signal amplifier part into the form of an exponential function, processing the video signal into the form of a reverse function thereafter, and outputting the video signal in the form of a converted hyperbolic tangent function; and a signal adjuster part adjusting a voltage level of the converted video signal according to the control signal from the micro-control unit.
According to another aspect of the present invention, the above and other objects maybe also achieved by the provision of a method for gamma correcting a video signal in a display apparatus, comprising the steps of selecting the amount of gamma correction; gamma correcting the video signal according to the selected correction amount; and displaying the gamma corrected video signal.
Desirably, the gamma correction step is comprised of sectioning the video signals into a plurality of sections depending upon voltage levels of the video signals, receiving the video signal having a predetermined upper limit or less and amplifying it; converting the video signal amplified into the form of an exponential function, processing the video signal into the form of a reverse function thereafter, and outputting the video signal in the form of a converted hyperbolic tangent function; amplifying the converted video signal according to the selected gamma correction amount; and composing the amplified video signal.